In order to remove security vulnerability in an IP-SAN and eliminate unauthorized access by spoofing, firewalls are installed in valid user servers and storage devices, and a distributed firewall manager for managing the firewalls integrally is provided in the IP-SAN. The distributed firewall manager obtains discovery domain information from an iSNS server, determines nodes registered in the iSNS server as the nodes of valid users, and autocreates a security policy according to sets consisting of an iSCSI name and portal information. This security policy is distributed to all of the firewalls as a common policy, whereupon access control is executed to deny TCP connection requests from unauthorized access sources.